Mixed-valent states in the redox chemistry of double- and triple-decker-sandwich free base and copper porphyrins

Double- and triple-decker-sandwich free base and copper porphyrins, where tetraphenylporphyrin rings are linked together by two urea bridges, have been studied by cyclicvoltammetry and UV-vis spectroelectrochemistry. Mixed-valent states appear in all cases, even with dimers and trimers containing twice or thrice the same porphyrin. The separations between the standard potentials in the H 2 -H 2 , Cu-Cu, H 2 -Cu dimers as well as in the H 2 -H 2 -H 2 , Cu-Cu-Cu, H 2 -Cu-H 2 trimers are interpreted in terms of Coulombic repulsion and interaction with the counter cations